THE PTERIDOPHYTA : LYCOPSIDA, ETC. 



573 



irregular upper face are made up of parenchyma, which also forms a prominent 

 rim round the top. Unicellular rhizoids are formed on the under surface. 

 All the top surface is devoted to the production of the sex organs. It is 



PiG. s^i-—Lycopocliia„. Origin of the sporangium A Superficial 

 group of initial cells. B, Archesporial mother cell. C Develop- 

 ment of archesponum and beginning of sporangiophore. U, 

 Tangential section of voung sporangium at shghtly later stage 

 than B, showing curved row of archesporial mother cells 

 E Sporangium initial in radial section showing three rows ot 

 archesporial mother cells. A to D, L. selago. E, L. claz^tum. 

 {After Bozver.) 



Fig .Sz.-Lvcopodiuu, clavatum. Side and top aspects of mature prothallus showing 

 numerous antheridia and rhizoids. {After Lang.) 



called the generative tissue, and its cells contain no food reserves and remain 

 for some time meristematic. The antheridia develop in the median portion 

 and the archegonia towards the outer rim. The development is centripetal. 

 The mode of nutrition of the prothallus is remarkable. The cells ot the 

 cortex and the palisade cells are filled with fungal hyphae, and these form 

 what is termed a mycorrhizal association with the cells of the prothallus. 



